STANGTRAIN,
Lionel did the Southern Pacific A-6 Atlantic engines in the 2018 Volume 2 catalog. They were delivered around August/September 2019. One if which was decorated in UP Grey Model # 1931180. It may not be 100% prototypical it is a real nice engine as my friend Ray has one. You should be able to find one of the forum sponsors that has one. Try Nicholas Smith first he usually has a good selection.
JohnB